This invention has relation to a device for inverting piles of paper supported on pallets. In the process of printing sheets of paper on both sides, the sheets, after being printed on a first side, come from the printing press and are deposited rapidly in vertical piles on pallets with the ink being initially somewhat wet. Slip sheets may or may not be used. Alignment of the papers must be maintained, slippage between individual sheets of paper minimized, and the pile of papers must be inverted so that the individual sheets can be fed into the same or a second printing press for printing on the other side.
Without mechanical aids, it is necessary that portions of the pile or stack be manually removed and inverted successively to form a second pile or stack. This is time consuming; there tends to be an undue amount of sliding of adjacent sheets with respect to each other causing ink smear; and the different portions of the stack are not likely to be accurately aligned.
Excessively large and extremely expensive mechanical means have been devised to move under a pallet, lift the pallet and the paper stack thereon, clamp an inverted pallet on top of the stack, invert the pallets and stack, and lower the inverted stack to the ground supported on the formerly upper pallet. See, for example, U.S. Pat. No. 2,520,252 granted to G. C. Mutchler, in August of 1950. While it is possible that such extremely expensive mechanisms can make economic sense in certain very large printing operations, it is evident that such a means for inverting paper piles is completely out of the reach financially of the operator of a small or medium-size print shop. Also, such elaborate structures lack the portability which is often necessary or at least extremely desirable, as when several paper piles are to be run on one side, and stored for an indefinite period, before the same press is to be utilized to run these same paper piles on the second side.
It is known to lift a paper pile and pallet with a fork lift truck or the like; to put an inverted pallet on the top of such lifted paper pile; to slide a C-shape frame mounted within a partial hoop under and over the two spaced-apart pallets and the paper pile; to clamp the inverted pallet down against the paper pile by using studs mounted in the upper outer arm of the C-frame; to remove the fork lift truck; to roll the hoop to invert the paper pile and the pallets; to use the lift truck to elevate the once inverted, now upright, pallet and the paper pile; to pull the C-frame/hoop arrangement away from the inverted pile and pallets; and to use the fork lift to lower the inverted pile and pallets to the ground. See U.S. Pat. No. 2,769,557 to N. T. Ohr, granted in November of 1956.
Obviously this elaborate mechanism of the Ohr patent is outside of the cost effective range of all small and medium-sized printing operations and of all but the largest of operators. Unless there is some other purpose for a lift truck, it is very inefficient to have one on hand only for this purpose. If the lift truck were to be used for something else, it would obviously often cause delays in inverting paper piles when needed. Furthermore, the floor space required in the print shop to rotate the hoop through 180.degree. and then to turn it over to reposition the fork lift truck to approach the hoop and inverted pile from the opposite direction limits the usefulness of this device.
Another device for inverting paper piles is shown in U.S. Pat. No. 3,738,519 to J. D. Edwards, granted in June of 1973. In this device, head mounted arms are provided to extend under the bottom pallet and above an inverted top pallet sandwiching a pile of papers to be inverted, the arms are moved together with great force to insure that papers cannot fall out of the pile or become misaligned, and then the pile is inverted, not by being rotated back to lie on one edge, but by being rotated with respect to the horizontal axis of rotation of the head mounted on a vertical stanchion. The pile being unsupported except by the force exerted by the two sets of clamping arms toward each other when the pile is in its one-half rotation position.
This structure also is unduly complicated and expensive. Because it relies on compression of the papers in the pile for its holding action, it is completely unsatisfactory except in situations where the ink has become thoroughly dried. Thus, for all practical purposes, it is unuseable in a modern print shop where the time between printing of the pile on one side and the beginning of the printing of the pile on the second side must be kept to an absolute minimum for efficiency and economy of operation.
Apparatus to invert other goods employing upper and lower clamps which are rotated about horizontal axes passing through vertically supported rotating heads is known. See U.S. Pat. No. 3,895,922 granted to D. E. Pluntz in July of 1975 for inverting boxes.
Devices to slide under pallets which support heavy articles and then to rotate those articles through only 90.degree. by utilizing one-quarter of a hoop is known. See U.S. Pat. No. 2,251,731 to E. G. Daniels, granted in August of 1941 for rotating upright tobacco hogs heads weighing one thousand pounds (453.6 kg) to positions on their sides.
A preliminary patent search was conducted on this invention, and the only patents cited are the five set out above.
Applicant and those in privity with applicant know of no closer prior art than that discussed above.